[Objective] This study aimed to investigate the correlation between stigma characteristics and outcrossing rate of photo-thermo sensitive genic male sterile（PTGMS） rice lines. [Method] The stigma exsertion rate, stigma size and stigma vitality of Chuang 5S, Yun 9S, Peiai 64 S, P88 S and Y58 S were analyzed. Using R608 as a male parent, outcrossing rate of these five PTGMS lines was determined. [Result]There were differences in stigma exsertion rate, stigma size and stigma vitality among five PTGMS lines. P88 S exhibited the best stigma characteristics and relatively strong stigma vitality, with the stigma exsertion rate of 95.94%, stigma vitality coefficient of 2.71, outcrossing rate of 84.02% in the field. Peiai 64 s had the minimum stigma length（2.41 mm） and stigma width（1.10 mm） and the weakest stigma vitality, with the stigma exsertion rate of 93.04%, outcrossing rate of 65.47%. Yun 9S,Y58 S and Chuang 5S displayed medium stigma characteristics, among which Yun9 S exhibited higher outcrossing rate than other two PTGMS lines. Correlation analysis showed that stigma exsertion rate, stigma length, stigma width, stigma area and stigma volume were significantly correlated to outcrossing rate（P〈0.05）, with correlation coefficients of 0.897, 0.934, 0.934, 0.939 and 0.937, respectively. However,there was no significant correlation between stigma vitality coefficient and outcrossing rate. [Conclusion] Based on stigma characteristics of five PTGMS lines, auxiliary pollination measures should be adopted reasonably to save production costs and improve hybrid rice seed yield.
